1. Field of the Invention
The present invention relates to an optical mouse and, more particularly to an optical mouse having image light sources with different colors.
2. Description of the Related Art
In general, an optical mouse is designed to detect movement of an image carried by a light reflected from a mouse pad (or a reflection surface) on which the optical mouse is moved, thereby causing a cursor on an associated display screen, to be moved in accordance with the movement of the mouse. Since such an optical mouse has advantages of the accuracy of its motion detection, and smoothness in its motion, as compared with the prior art ball-type mouse, its use is gradually increasing.
FIG. 1 is an illustration of a typical optical mouse. Such an optical mouse includes a printed circuit board 10a, a red Light Emitting Diode (LED) 20a disposed on the printed circuit board 10a for emitting red light, a photodetector unit 30a for detecting the image formed on the mouse pad (or the reflection surface) due to the red light emitted thereto, and an optical element 40a having a light-guiding unit 41a and a lens unit 42a. The light-guiding unit 41a can guide the red light emitted from the red LED 20a for irradiating the reflection surface with a bright light. The lens unit 42a can converge a reflected light reflected by the reflection surface into a photodetector unit 30a. The image detected at the optical sensor 30a is input into the printed circuit board 10a through lead frames where it is converted to an electrical signal, thus enabling the cursor to be moved on the display screen by movement of the mouse.
However, the conventional optical mouse still has disadvantages as follows. When the optical mouse is designed to provide only one red light source carrying the red image on the green reflection surface, the light-reflection rate of the red image will be lower relative to the green reflection surface because red is the complementary color for green. Therefore, the red image is greatly absorbed by the green reflection surface, causing the detected quantity of the red light to be lower, so as to produce a “color blindness” phenomenon. As described above, the sensitivity of the optical mouse will be greatly reduced to point of being nonfunctional. In order to eliminate the aforesaid disadvantages, a high sensitivity photodetector unit is provided, or a high power red LED, but this increases component costs and makes manufacturing difficult.